population so pressing that they may be willing to forego the economic and social benefits of reducing fertility. We urge that in these nations the leaders (a) make themselves thoroughly aware of the demographic dynamics of their country and its interrelations with economic and social development, and give adequate attention to population growth and change in formulating development policies; and (b) examine closely the extent to which the substantial penalties to development that result from high fertility and rapid population growth and the benefits of reduced fertility and slower rates of growth may apply in the special circumstances of their country now and in the next 2 or 3 decades. Even a marked reduction in rates of population growth to the levels suggested later in this chapter will result in a doubling of population size in less than 50 years. Asymmetries in Population Policy There is a considerable asymmetry in the possible range of population policies for less developed countries. Policies to accelerate mortality declines are feasible and may be desirable, but on both humanitarian and political grounds no option exists either to increase mortality or to abandon efforts for further mortality reduction. Policies to reduce fertility are feasible and desirable, but policies to increase fertility significantly are not feasible because birth rates are already at a high level. Internal migration from the countryside to towns and cities is widespread in developing countries and may be subject to modification by policy, but except for certain special situations such as emigration from islands with limited resources, and emigration to alleviate political or ethnic conflicts, sustained international migration on a sufficiently large scale is neither politically feasible nor economically reasonable as a solution to population problems. Though greater freedom of international migration throughout the world is desirable from many points of view, it cannot now contribute very much to alleviating the effects of population growth, because the size of the earth's population is now increasing so rapidly. The total number of people who emigrated from Europe and Asia to North and South America and Oceania during the 19th and early 20th centuries was about 60 million. This is less than 1 year's increase in the world's population at the present time. Transocean air and water transportation facilities have become very much greater during the past 50 years, and the aircraft and ships now exist to move this large number of people across the oceans each year. But even with enormous capital investments for education, job creation, housing, and other social infrastructures, it would probably be impossible for present sparsely populated countries to assimilate in their existing economies and societies the number of migrants required to offset significantly the problems of population growth in more crowded countries.